Remember the 5 different Gmail Notifiers for Windows? Here is another one, but this one is especially for Windows 7 and it looks awesome.
The Gmail Notifier Plus pins to Windows 7’s superbar like any other application. It allows you to get previews of your inbox from the preview window which pop-ups when you move the mouse pointer over the icon. Clicking on the middle button opens the mail in Gmail.
It also integrates with the jump list and your unread mails are accessible from it.
Gmail Notifier Plus can retrieve mails from only a single account including Google Apps account. The notifier uses Gmail’s secured RSS feed to retrieve the mails and the username and password are stored using a machine's dependent encryption, so it’s pretty safe.